Influence of maximum range of motion and stiffness on the viscoelastic stretch response

Introduction We examined the influence of maximum range of motion (MROM) and passive stiffness on the viscoelastic stretch response. Methods Four 30-s constant-angle passive stretches of the plantar flexors at a predetermined torque were performed to determine the rate and relative change in stress relaxation (decline in torque during each 30-s stretch) and creep (increase in ankle joint angle across all 4 stretches). Stress relaxation and creep responses were examined between participants after they were ranked into high and low groups based on MROM and passive stiffness values. Results Stress relaxation responses were unaffected by MROM and passive stiffness; however, creep was influenced by differences in passive stiffness but not MROM. Conclusions Passive stiffness but not MROM influences the acute viscoelastic response to passive stretching. Participants with less stiff plantar flexors experience greater increases in range of motion when they are stretched at a constant torque